Electrosurgical devices, directional reflector assemblies coupleable thereto, and electrosurgical systems including same

ABSTRACT

A directional reflector assembly includes a tubular shaft having a proximal end and a distal end and adapted to operably engage an electrosurgical ablation probe, and a conical aperture having a proximal open apex joined to a distal end of the tubular shaft, and a distal open base, wherein an interior volume of the tubular shaft is open to the conical aperture.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a division of U.S. patent application Ser.No. 14/564,946, filed on Dec. 9, 2014, which is a continuation of U.S.patent application Ser. No. 12/568,524, filed on Sep. 28, 2009, now U.S.Pat. No. 8,906,007, the entire disclosures of each of the foregoingapplications are incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to electrosurgical devices suitable foruse in tissue ablation applications and, more particularly, toelectrosurgical devices, directional reflector assemblies coupleablethereto, and electrosurgical systems including the same.

2. Discussion of Related Art

Treatment of certain diseases requires the destruction of malignanttissue growths, e.g., tumors. Electromagnetic radiation can be used toheat and destroy tumor cells. Treatment may involve inserting ablationprobes into tissues where cancerous tumors have been identified. Oncethe probes are positioned, electromagnetic energy is passed through theprobes into surrounding tissue.

In the treatment of diseases such as cancer, certain types of tumorcells have been found to denature at elevated temperatures that areslightly lower than temperatures normally injurious to healthy cells.Known treatment methods, such as hyperthermia therapy, heat diseasedcells to temperatures above 41° C. while maintaining adjacent healthycells below the temperature at which irreversible cell destructionoccurs. These methods involve applying electromagnetic radiation toheat, ablate and/or coagulate tissue. Microwave energy is sometimesutilized to perform these methods. Other procedures utilizingelectromagnetic radiation to heat tissue also include coagulation,cutting and/or ablation of tissue.

Electrosurgical devices utilizing electromagnetic radiation have beendeveloped for a variety of uses and applications. A number of devicesare available that can be used to provide high bursts of energy forshort periods of time to achieve cutting and coagulative effects onvarious tissues. There are a number of different types of apparatus thatcan be used to perform ablation procedures. Typically, microwaveapparatus for use in ablation procedures include a microwave generatorthat functions as an energy source, and a microwave surgical instrument(e.g., microwave ablation probe) having an antenna assembly fordirecting the energy to the target tissue. The microwave generator andsurgical instrument are typically operatively coupled by a cableassembly having a plurality of conductors for transmitting microwaveenergy from the generator to the instrument, and for communicatingcontrol, feedback and identification signals between the instrument andthe generator.

There are several types of microwave probes in use, e.g., monopole,dipole and helical, which may be used in tissue ablation applications.In monopole and dipole antenna assemblies, microwave energy generallyradiates perpendicularly away from the axis of the conductor. Monopoleantenna assemblies typically include a single, elongated conductor. Atypical dipole antenna assembly includes two elongated conductors thatare linearly aligned and positioned end-to-end relative to one anotherwith an electrical insulator placed therebetween. Helical antennaassemblies include helically-shaped conductor configurations of variousdiameters and dimensions. The main modes of operation of a helicalantenna assembly are normal mode (broadside), in which the fieldradiated by the helix is maximum in a perpendicular plane to the helixaxis, and axial mode (end fire), in which maximum radiation is along thehelix axis.

A microwave transmission line typically includes a long, thin innerconductor that extends along the longitudinal axis of the transmissionline and is surrounded by a dielectric material and is furthersurrounded by an outer conductor around the dielectric material suchthat the outer conductor also extends along the transmission line axis.In one variation of an antenna, a waveguiding structure, such as alength of transmission line or coaxial cable, is provided with aplurality of openings through which energy “leaks” or radiates away fromthe guiding structure. This type of construction is typically referredto as a “leaky coaxial” or “leaky wave” antenna.

Cooling the ablation probe may enhance the overall heating pattern ofthe antenna, prevent damage to the antenna and prevent harm to theclinician or patient. Because of the small temperature differencebetween the temperature required for denaturing malignant cells and thetemperature normally injurious to healthy cells, a known heating patternand precise temperature control is needed to lead to more predictabletemperature distribution to eradicate the tumor cells while minimizingthe damage to surrounding normal tissue.

During certain procedures, it can be difficult to assess the extent towhich the microwave energy will radiate into the surrounding tissue,making it difficult to determine the area or volume of surroundingtissue that will be ablated. In some instances, targeted lesions may belocated on or near the surface of the target organ. Such surface lesionshave been treated with invasive ablation needles or sticks, which maycause damage to adjacent anatomical structures, increase the likelihoodof hemorrhaging, and lengthen operative and recovery times.

SUMMARY

The present disclosure relates to a directional reflector assemblyincluding a tubular shaft having a proximal end and a distal end andadapted to operably engage an electrosurgical ablation probe, and aconical aperture having a proximal open apex joined to a distal end ofthe tubular shaft, and a distal open base, wherein an interior volume ofthe tubular shaft is open to the conical aperture.

The present disclosure also relates to a directional reflector assemblyincluding a tubular inner shaft having a proximal end and a distal endand adapted to operably engage an electrosurgical ablation probe, atubular outer shaft coaxially-disposed about the inner shaft to define afluid conduit therebetween, and a conical aperture having a proximalopen apex joined to a distal end of the tubular outer shaft, and adistal open base, wherein an interior volume of the tubular inner shaftis in fluid communication with the conical aperture.

The present disclosure also relates to an electrosurgical ablationsystem including a source of microwave ablation energy, a microwaveablation probe operably coupled to the source of microwave ablationenergy, wherein the microwave ablation probe includes a proximal handleportion and a distal shaft portion, and at least one protrusion disposedat a proximal end of the shaft that is adapted to operably engage a slotprovided by a directional reflector assembly.

The present disclosure also relates to a method of operating anelectrosurgical ablation system including the steps of providing asource of microwave ablation energy and providing a microwave ablationprobe adapted to operably coupled to the source of microwave ablationenergy, wherein the microwave ablation probe includes a proximal handleportion and a distal shaft portion. The method also includes the stepsof operably coupling a directional reflector assembly to the probe andactivating the source of microwave energy.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the presently disclosed electrosurgical devicesand directional reflector assemblies coupleable thereto will becomeapparent to those of ordinary skill in the art when descriptions ofvarious embodiments thereof are read with reference to the accompanyingdrawings, of which:

FIG. 1 is a schematic diagram of an ablation system in accordance withan embodiment of the present disclosure;

FIG. 2 is a partial, longitudinal cross-sectional view of an embodimentof the energy applicator of the ablation system shown in FIG. 1 inaccordance with the present disclosure;

FIG. 3 is an enlarged view of the indicated area of detail of FIG. 2according to an embodiment of the present disclosure;

FIG. 4 is a perspective view of an embodiment of a directional reflectorassembly in accordance with the present disclosure;

FIG. 5 is a partial, cross-sectional view of the energy applicator ofFIG. 2 shown operably associated with the directional reflector assemblyof FIG. 4;

FIG. 6 is a perspective view of another embodiment of a directionalreflector assembly in accordance with the present disclosure;

FIG. 7A is a partial, perspective view of the energy applicator of FIG.2 shown operably associated with the directional reflector assembly ofFIG. 6;

FIG. 7B is a partial, perspective view of the energy applicator anddirectional reflector assembly of FIG. 7A shown with a fastener elementcoupled to an attachment portion of the directional reflector assembly;

FIG. 8 is a perspective view of an embodiment of a directional reflectorassembly in accordance with the present disclosure that includes anadhesive-receiving recess;

FIG. 9 is a partial, cross-sectional view of the energy applicator ofFIG. 2 shown operably associated with the directional reflector assemblyof FIG. 8;

FIG. 10 is a cross-sectional view of the energy applicator of FIG. 2shown operably associated with an embodiment of a directional reflectorassembly in accordance with the present disclosure having a shellassembly including dielectric shells and an adhesive-receiving recess;

FIG. 11 is a perspective view of an embodiment of an energy applicatorin accordance with the present disclosure that includes an ablationprobe operably associated with a pistol-grip body and a male connectordisposed at the proximal end of the probe;

FIG. 12A is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a tubular portion having a female connector adapted forattachment to the male connector of the energy applicator of FIG. 11;

FIG. 12B is a bottom, perspective view of the directional reflectorassembly of FIG. 12A;

FIG. 13A is a perspective view of the energy applicator of FIG. 11 shownwith the directional reflector assembly of FIG. 12A mounted on the probeshaft thereof;

FIG. 13B is a bottom, perspective view of the energy applicator and thedirectional reflector assembly of FIG. 13A;

FIGS. 14A through 14C are perspective views of alternative embodimentsof the directional reflector assembly of FIG. 12A;

FIG. 15 is a side view of an ablation probe in accordance with thepresent disclosure having an alignment protrusion at a proximal end of aprobe shaft thereof;

FIG. 16 is a side view of the ablation probe of FIG. 15 shown with adirectional reflector assembly in accordance with the present disclosuremounted on the probe shaft;

FIG. 17 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure having anair-filled conical aperture;

FIG. 18 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure having adielectric-filled conical aperture;

FIG. 19 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a conical aperture having a plurality of dielectric layers;

FIG. 20 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a conical aperture having a plurality of dielectric layers andan end cap;

FIG. 21 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a cooled shaft and a conical aperture having a plurality ofdielectric layers;

FIG. 22 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a cooled shaft and a conical aperture having fluid- anddielectric-filled regions;

FIG. 23 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a cooled shaft and a coolant-filled conical aperture and an endcap;

FIG. 24 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a conical aperture having fluid- and dielectric-filled regions;

FIG. 25 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a dielectric-filled conical aperture and a balun positionedover the shaft;

FIG. 26 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes an air-filled conical aperture and a balun positioned over theshaft and within the cone; and

FIG. 27 is a perspective view of an embodiment of a directionalreflector assembly in accordance with the present disclosure thatincludes a dielectric-filled conical aperture and a balun positionedover the shaft and within the cone.

DETAILED DESCRIPTION

Hereinafter, embodiments of the presently disclosed electrosurgicaldevices, directional reflector assemblies coupleable thereto, andelectrosurgical system including the same will be described withreference to the accompanying drawings. Like reference numerals mayrefer to similar or identical elements throughout the description of thefigures. As shown in the drawings and as used in this description, andas is traditional when referring to relative positioning on an object,the term “proximal” refers to that portion of the apparatus that iscloser to the user and the term “distal” refers to that portion of theapparatus that is farther from the user.

Electromagnetic energy is generally classified by increasing energy ordecreasing wavelength into radio waves, microwaves, infrared, visiblelight, ultraviolet, X-rays and gamma-rays. As it is used in thisdescription, “microwave” generally refers to electromagnetic waves inthe frequency range of 300 megahertz (MHz) (3×10⁸ cycles/second) to 300gigahertz (GHz) (3×10¹¹ cycles/second). As it is used in thisdescription, “ablation procedure” generally refers to any ablationprocedure, such as microwave ablation, radio frequency (RF) ablation ormicrowave ablation assisted resection. As it is used in thisdescription, “transmission line” generally refers to any transmissionmedium that can be used for the propagation of signals from one point toanother.

Various embodiments of the present disclosure provide electrosurgicaldevices operably associated with directional reflector assemblies fortreating tissue and methods of directing electromagnetic radiation to atarget volume of tissue. Embodiments may be implemented usingelectromagnetic radiation at microwave frequencies or at otherfrequencies. An electrosurgical system including an energy applicatoroperably associated with a directional reflector assembly, according tovarious embodiments, is designed and configured to operate between about500 MHz and about 10 GHz with a directional radiation pattern.

Various embodiments of the presently disclosed electrosurgical devices,directional reflector assemblies coupleable thereto and electrosurgicalsystem including the same are suitable for microwave ablation and foruse to pre-coagulate tissue for microwave ablation assisted surgicalresection. Although various methods described hereinbelow are targetedtoward microwave ablation and the complete destruction of target tissue,it is to be understood that methods for directing electromagneticradiation may be used with other therapies in which the target tissue ispartially destroyed or damaged, such as, for example, to prevent theconduction of electrical impulses within heart tissue. In addition,although the following description describes the use of a dipolemicrowave antenna, the teachings of the present disclosure may alsoapply to a monopole, helical, or other suitable type of microwaveantenna.

FIG. 1 shows an electrosurgical system 10, according to an embodiment ofthe present disclosure that includes an energy applicator or probe 100.Probe 100 generally includes an antenna assembly 12 having a radiatingportion connected by a feedline 110 (or shaft) via a transmission line15 to a connector 16, which may further operably connect the probe 100to an electrosurgical power generating source 28, e.g., a microwave orRF electrosurgical generator.

Feedline 110 may be formed from any suitable flexible, semi-rigid orrigid microwave conductive cable and may connect directly to anelectrosurgical power generating source 28. Alternatively, the feedline110 may electrically connect the antenna assembly 12 via thetransmission line 15 to the electrosurgical power generating source 28.Feedline 110 may have a variable length from a proximal end of theantenna assembly 12 to a distal end of transmission line 15 ranging froma length of about one inch to about twelve inches. Feedline 110 may beformed of suitable electrically conductive materials, e.g., copper,gold, silver or other conductive metals having similar conductivityvalues. Feedline 110 may be made of stainless steel, which generallyoffers the strength required to puncture tissue and/or skin. Conductivematerials used to form the feedline 110 may be plated with othermaterials, e.g., other conductive materials, such as gold or silver, toimprove their properties, e.g., to improve conductivity, decrease energyloss, etc. In some embodiments, the feedline 110 includes stainlesssteel, and to improve the conductivity thereof, the stainless steel maybe coated with a layer of a conductive material such as copper or gold.Feedline 110 may include an inner conductor, a dielectric materialcoaxially surrounding the inner conductor, and an outer conductorcoaxially surrounding the dielectric material. Antenna assembly 12 maybe formed from a portion of the inner conductor that extends distal ofthe feedline 110 into the antenna assembly 12. Feedline 110 may becooled by fluid e.g., saline or water, to improve power handling, andmay include a stainless steel catheter.

In some embodiments, the power generating source 28 is configured toprovide microwave energy at an operational frequency from about 500 MHzto about 2500 MHz. In other embodiments, the power generating source 28is configured to provide microwave energy at an operational frequencyfrom about 500 MHz to about 10 GHz. Power generating source 28 may beconfigured to provide various frequencies of electromagnetic energy.Transmission line 15 may additionally, or alternatively, provide aconduit (not shown) configured to provide coolant from a coolant source18 to the probe 100.

Located at the distal end of the antenna assembly 12 is an end cap ortapered portion 120 that may terminate in a sharp tip 123 to allow forinsertion into tissue with minimal resistance. The end cap or taperedportion 120 may include other shapes, such as, for example, a tip 123that is rounded, flat, square, hexagonal, or cylindroconical.

In some variations, the antenna assembly 12 includes a distal radiatingportion 105 and a proximal radiating portion 140. A junction member 130may be provided. Junction member 130, or portions thereof, may bedisposed between the proximal and distal radiating portions, 140 and105, respectively. In some embodiments, the distal and proximalradiating portions 105, 140 align at the junction member 130, which isgenerally made of a dielectric material, e.g., adhesives, and are alsosupported by the inner conductor that extends at least partially throughthe distal radiating portion 105. Junction member 130 may be formed fromany suitable elastomeric or ceramic dielectric material by any suitableprocess. In some embodiments, the junction member 130 is formed byover-molding and includes a thermoplastic elastomer, such as, forexample, polyether block amide (e.g., PEBAX®, manufactured by The ArkemaGroup of Colombes, France), polyetherimide (e.g., ULTEM® and/or EXTEM®,manufactured by SABIC Innovative Plastics of Saudi Arabia) and/orpolyimide-based polymer (e.g., VESPEL®, manufactured by E. I. du Pont deNemours and Company of Wilmington, Del., United States). Junction member130 may be formed using any suitable over-molding compound by anysuitable process, and may include use of a ceramic substrate.

In some embodiments, the antenna assembly 12 may be provided with acoolant chamber (not shown). Additionally, the junction member 130 mayinclude coolant inflow and outflow ports (not shown) to facilitate theflow of coolant into, and out of, the coolant chamber. Examples ofcoolant chamber and coolant inflow and outflow port embodiments aredisclosed in commonly assigned U.S. patent application Ser. No.12/401,268 filed on Mar. 10, 2009, entitled “COOLED DIELECTRICALLYBUFFERED MICROWAVE DIPOLE ANTENNA”, and U.S. Pat. No. 7,311,703,entitled “DEVICES AND METHODS FOR COOLING MICROWAVE ANTENNAS”.

In some embodiments, the antenna assembly 12 may be provided with anouter jacket (not shown) disposed about the distal radiating portion105, the junction 130 and/or the proximal radiating portion 140. Theouter jacket may be formed of any suitable material, such as, forexample, polymeric or ceramic materials. The outer jacket may be appliedby any suitable method, such as, for example, heat shrinking,over-molding, coating, spraying dipping, powder coating, baking and/orfilm deposition. The outer jacket may be a water-cooled catheter formedof a material having low electrical conductivity.

During microwave ablation, e.g., using the electrosurgical system 10,the probe 100 is inserted into or placed adjacent to tissue andmicrowave energy is supplied thereto. Ultrasound or computed tomography(CT) guidance may be used to accurately guide the probe 100 into thearea of tissue to be treated. Probe 100 may be placed percutaneously orsurgically, e.g., using conventional surgical techniques by surgicalstaff. A clinician may pre-determine the length of time that microwaveenergy is to be applied. Application duration may depend on many factorssuch as tumor size and location and whether the tumor was a secondary orprimary cancer. The duration of microwave energy application using theprobe 100 may depend on the progress of the heat distribution within thetissue area that is to be destroyed and/or the surrounding tissue.Single or multiple probes 100 may provide ablations in short proceduretimes, e.g., a few minutes, to destroy cancerous cells in the targettissue region.

A plurality of probes 100 may be placed in variously-arrangedconfigurations to substantially simultaneously ablate a target tissueregion, making faster procedures possible. Multiple probes 100 can beused to synergistically create a large ablation or to ablate separatesites simultaneously. Tissue ablation size and geometry is influenced bya variety of factors, such as the energy applicator design, number ofenergy applicators used simultaneously, time and wattage.

In operation, microwave energy having a wavelength, lamda (A), istransmitted through the antenna assembly 12, e.g., along the proximaland distal radiating portions 140, 105, and radiated into thesurrounding medium, e.g., tissue. The length of the antenna forefficient radiation may be dependent on the effective wavelength A_(eff)that is dependent upon the dielectric properties of the medium beingradiated. Antenna assembly 12 through which microwave energy istransmitted at a wavelength A may have differing effective wavelengthsλ_(eff) depending upon the surrounding medium, e.g., liver tissue, asopposed to breast tissue.

Referring to FIGS. 2 and 3, an embodiment of the antenna assembly 12 ofFIG. 1 is shown and includes an inner conductor 210, an outer conductor260, and may include a first dielectric material 240 separating theinner conductor 210 and the outer conductor 260. In some embodiments,the inner conductor 210 is formed from a first electrically conductivematerial (e.g., stainless steel) and the outer conductor 260 is formedfrom a second electrically conductive material (e.g., copper). In someembodiments, the outer conductor 260 coaxially surrounds the innerconductor 210 along a distal portion of the antenna assembly 12, e.g.,as shown in FIG. 2. Inner conductor 210 and the outer conductor 260 maybe formed from any suitable electrically conductive material.

First dielectric material 240 may be formed from any suitable dielectricmaterial, including, but not limited to, ceramics, water, mica,polyethylene, polyethylene terephthalate, polyimide,polytetrafluoroethylene (a.k.a. PTFE or Teflon®, manufactured by E. I.du Pont de Nemours and Company of Wilmington, Del., United States),glass, or metal oxides. Antenna assembly 12 may be provided with asecond dielectric material 29 surrounding the outer conductor 260 and/orthe puck 130, or portions thereof. Second dielectric material 29 may beformed from any suitable dielectric material. In some embodiments, thesecond dielectric material 29 is formed from a material with adielectric constant different than the dielectric constant of the firstdielectric material 240.

In some embodiments, the antenna assembly 12 includes a conductor endportion 280, which may be formed from any suitable electricallyconductive material. In some embodiments, the conductor end portion 280is coupled to the inner conductor 210 and may be formed of the samematerial as the inner conductor 210. As shown in FIG. 2, the conductorend portion 280 may be spaced apart from the outer conductor 260 by thepuck 130 disposed therebetween. Tapered region 120, or portions thereof,may surround a proximal portion of the conductor end portion 280. Insome embodiments, the conductor end portion 280 is substantiallycylindrically shaped, and may be formed from stainless steel. The shapeand size of the conductor end portion 280 may be varied from theconfiguration depicted in FIG. 2. In some embodiments, at least aportion of the conductor end portion 280 is surrounded by the seconddielectric material 29.

FIG .4 shows a directional reflector assembly 500 according to anembodiment of the present disclosure that includes a shell assembly 510,a first attachment portion 520 disposed at the distal end portion 501 ofthe shell assembly 510, and a second attachment portion 530 that extendsproximally from the proximal end 502 of the shell assembly 510. Firstattachment portion 520 may have a substantially conical shape, and maybe formed of any suitable material, such as metal. Second attachmentportion 530 may have a substantially cylindrical shape, and may beformed of any suitable material, such as a generally flexible andresilient thermoplastic material and/or metal. In embodiments, thesecond attachment portion 530 may be replaceable (e.g., removeablycoupleable to the shell assembly 510, such as by a threaded fastener),thereby providing the capability to use second attachment portions 530of different diameters to accommodate varied ablation probe diameters.

Shell assembly 510 may be shaped in such a manner to provide a desiredsurface ablation shape as well as aid in impedance matching. Forexample, the shell assembly 510 may taper from a diameter similar to thediameter of the second attachment portion 530 to a larger diameter asthe shell assembly 510 extends proximally. Shell assembly 510 may haveany suitable shape and may be designed for tight spaces encounteredduring surgical operations. For example, the shell assembly 510 may havea shape similar to the shape of a thick butter knife (e.g., 921 shown inFIG. 14A) or a half-conical shape (e.g., 931 shown in FIG. 14B).

As shown in FIGS. 4 and 5, the shell assembly 510 generally includes anouter portion 511 and an inner portion 512, and may include a recess inthe form of a groove “G” defined in the planar surface “S” of the innerportion 512 generally configured to receive a portion of an energyapplicator therein. As shown in FIG. 5, a portion of the antennaassembly 12 (e.g., distal radiating portion 105 and proximal radiatingportion 140) may be disposed within the groove “G” in the inner portion512.

Outer portion 511 may include an electrically conductive material, suchas, for example, copper, stainless steel, titanium, titanium alloys suchas nickel-titanium and titanium-aluminum-vanadium alloys, aluminum,aluminum alloys, tungsten carbide alloys or combinations thereof.Portions of the outer portion 511 may be loaded with low- to mid-rangepermittivity dielectric materials to aid in radiation directivity andimpedance matching. In general, the dielectric permittivity wouldincrease in value with radial distance from the electrically-conductivemember 511. Several shells, or other shapes, of different dielectricmaterials may nest together to form the outer portion 511.

Inner portion 512 may include a dielectric material. In someembodiments, the inner portion 512 includes dielectric material layers.For example, the inner portion 512 may include one or more thin layers,one or more thick layers or a mixture of thick and thin layers. Innerportion 512 may be composed of any suitable dielectric material whichmay be the same as, or different from, the dielectric material, if any,used in the outer portion 511. The dielectric materials used to form theinner portion 512 may vary in dielectric constant with shells (e.g.,7171, 7172 and 7173 shown in FIG. 10) or more complex dielectriclayering to achieve the optimum antenna directivity and energy to tissuedelivery. In embodiments, the dielectric material used to form the innerportion 512 may have a relatively high dielectric constant k (e.g.,k≈80) to enhance the directional influence of the electromagnetic field.

First and second attachment portions, 520 and 530, may be formed of anysuitable material, such as metal. In embodiments, the second attachmentportion 530 includes a tubular body 531 defining a lumen 534 into whicha proximal portion of the antenna assembly 12 may be positioned. Tubularbody 531 may be provided with an inner liner (not shown) disposed incontact with the inner surface 535, or portion thereof, of the lumen534, wherein the inner liner is configured to frictionally engage atleast a portion of the outer surface of an energy applicator shaftdisposed within the lumen 534 when the directional reflector assembly500 is operably associated with the energy applicator. An outer sleeve(not shown) may additionally, or alternatively, be provided to at leasta portion of an energy applicator, wherein the outer sleeve is adaptedto frictionally engage the inner surface 535 of the lumen 534. Inembodiments, the second attachment portion 530, or portion thereof, isformed of a generally flexible and/or resilient material, e.g., siliconrubber, and may be provided with a fastener element (e.g., 660 shown inFIG. 7B) disposed around the outer surface thereof, e.g., forreleaseably securing a proximal portion of an energy applicator disposedwithin the lumen 534.

First attachment portion 520 generally includes a body 521 defining achamber 524 therein and an opening in communication with the groove “G”.Opening 523 and the chamber 524 are generally configured to receive thedistal end portion of an energy applicator, e.g., tip 123 of the antennaassembly 12. The shape and size of the first and second attachmentportions, 520 and 530, may be varied from the configuration depicted inFIG. 4.

FIG. 6 shows a directional reflector assembly 600 according to anembodiment of the present disclosure that includes a shell assembly 610,a first attachment portion 620, and a second attachment portion 640.Shell assembly 610 generally includes an outer portion 611 and an innerportion 612, and may include a recess in the form of a groove “G”defined in the planar surface “S” of the inner portion 612 generallyconfigured to receive a portion of an energy applicator therein. Shellassembly 610 is similar to the shell assembly 510 shown in FIG. 4, andfurther description thereof is omitted in the interests of brevity.

First attachment portion 620 generally includes a body 621 defining achamber 624 therein and an opening in communication with the groove “G”defined in the inner portion 612. First attachment portion 620 issimilar to the first attachment portion 520 shown in FIG. 4, and furtherdescription thereof is omitted in the interests of brevity.

Second attachment portion 640 extends proximally from the proximal endof the shell assembly 610. Second attachment portion 640 is similar tothe second attachment portion 530 shown in FIG. 4, except for its shape.In embodiments the second attachment portion 640 includes a body 641having a partial, cylindrical shape (e.g., a partial cylinder with asubstantially C-shaped cross section) of any suitable length. Secondattachment portion 640 may be formed of any suitable rigid, semi-rigidor flexible material, including, but not limited to, rubber, metal,polymeric materials, and combinations thereof.

FIG. 7A shows the antenna assembly 12 of FIG. 2 operably associated withthe directional reflector assembly 600 of FIG. 6. As shown in FIG. 7B,the second attachment portion 640 may be provided with a fastenerelement 660 generally adapted for releaseably closing the partial,cylindrically-shaped fastener element 660 around a proximal portion ofthe antenna assembly 12. Fastener element 660 may include any suitablefastener, such any suitable releasable fastener, coupleable to at leasta portion of the outer surface of the second attachment portion 640. Inembodiments, the fastener element 660 may include adhesive tape, wire,plastic tie cinch straps or other suitable tongue and groove typeelongated flexible plastic fasteners, metal clips, plastic clips, fabricor plastic straps, VELCRO™ hook and loop brand type tapes, etc.

FIG. 8 shows a directional reflector assembly 700 according to anembodiment of the present disclosure that includes a shell assembly 710.Shell assembly 710 generally includes an outer portion 711 and an innerportion 717, and may include a recess in the form of a groove “G”defined in the planar surface “S” of the inner portion 717. Outerportion 711 is similar to the outer portion 511 shown in FIG. 4, andfurther description thereof is omitted in the interests of brevity.

Groove “G” is generally configured to receive a portion of an energyapplicator therein. In embodiments, the groove “G” includes anadhesive-receiving recess 736 for receiving an adhesive material (e.g.,“A” shown in FIG. 10) therein. Recess 736 may be any suitable shape, andmay extend along the longitudinal axis of the groove “G”. Inembodiments, the length, depth and/or volume of the recess 736 may vary,e.g., depending on the material properties of the adhesive material “A”to be provided therein. In embodiments, the recess 736 may be single,elongated recess or a plurality of recesses.

FIGS. 9 and 10 show the antenna assembly 12 of FIG. 2 operablyassociated with the directional reflector assembly 700 of FIG. 8. Asshown in FIG. 10, the inner portion 717 of the shell assembly 710 may beformed of a first dielectric layer 7171, a second dielectric layer 7172and a third dielectric layer 7173. Inner portion 717 may include anysuitable number of dielectric layers in varied configurations. A varietyof dielectric materials may suitably be used, including, but not limitedto, polymers, ceramics, metal oxides and combinations thereof. Inembodiments, the dielectric material used to form the third dielectriclayer 7173 may have a relatively low dielectric constant k, such as k≈4.The thicknesses and dielectric constant k of the first, second and thirddielectric layers, 7171, 7172 and 7173, respectively, may be optimized,e.g., based on the desired frequency and desired field pattern, toablate an area of tissue to the desired depth.

FIG. 11 is a perspective view of an embodiment of an energy applicator800 in accordance with the present disclosure that includes apistol-grip body 850, a probe 860 extending distally therefrom., and amale connector 812 disposed at the proximal end of the ablation probe860. Pistol-grip body 850 is operably associated with the male connector812. In embodiments, the male connector 812 includes a retainer member811 that is movable between at least an engagement position and areleased position. In embodiments, the pistol-grip body 850 may includea user operable switch 815, e.g., a push button, operable to move themale connector 812 from an engagement position, in which the retainermember 811 is engaged with a female connector (e.g., 916 shown in FIGS.12A and 14A-14C), to a released position, in which the retainer member811 is disengaged from the female connector. The shape and size of themale connector 812 may be varied from the configuration depicted in FIG.11.

FIGS. 12A and 12B show an embodiment of a directional reflector assembly910 in accordance with the present disclosure that includes a shellassembly 917, a tubular portion 925 defining a lumen 934, and a femaleconnector 916 associated with the proximal end 905 of the tubularportion 925. Female connector 916 is adapted for engagement with themale connector 812 of the energy applicator 800 of FIG. 11.

Shell assembly 917 generally includes an outer portion 911 and an innerportion 912, and may include a recess 919 defined in the planar surface“S” of the inner portion 912 generally configured to receive a distalend portion of an energy applicator therein. Shell assembly 917 issimilar to the shell assembly 710 shown in FIG. 8, and furtherdescription thereof is omitted in the interests of brevity.

FIGS. 13A and 13B show the energy applicator of FIG. 11 with thedirectional reflector assembly of FIG. 12A mounted thereupon. As shownin FIGS. 13A and 13B, the lumen 934 is configured to receive theablation probe 860, whereby the distal portion 861 of the ablation probe860 extends across the planar surface “S” of the shell assembly 911.

FIG. 14A shows an embodiment of a directional reflector assembly 920 inaccordance with the present disclosure that includes a shell assembly927, a tubular portion 925 defining a lumen 934, and a female connector916 associated with the proximal end 905 of the tubular portion 925. Inembodiments, the shell assembly 927 has a paddle-like or thick butterknife shape, and may include a recess 929 defined in a planar surface“S” thereof. Shell assembly 927 is similar to the shell assembly 917shown in FIG. 12A, except for its shape, and further description thereofis omitted in the interests of brevity.

FIG. 14B shows an embodiment of a directional reflector assembly 930 inaccordance with the present disclosure that includes a shell assembly937, a tubular portion 925 defining a lumen 934, and a female connector916 associated with the proximal end 905 of the tubular portion 925. Inembodiments, the shell assembly 937 has a half-conical shape, and mayinclude a recess 939 defined in a planar surface “S” thereof. Shellassembly 937 is similar to the shell assembly 917 shown in FIG. 12A,except for its shape, and further description thereof is omitted in theinterests of brevity.

FIG. 14C shows an embodiment of a directional reflector assembly 940 inaccordance with the present disclosure that includes a shell assembly947, a tubular portion 925 defining a lumen 934, and a female connector916 associated with the proximal end 905 of the tubular portion 925. Inembodiments, the shell assembly 947 has a partial, cylindrical shape,and may include a recess 949 defined in a planar surface “S” thereof.Shell assembly 947 is similar to the shell assembly 917 shown in FIG.12A, except for its shape, and further description thereof is omitted inthe interests of brevity.

In another embodiment as shown in FIGS. 15 and 16, microwave ablationprobe 400 includes a handle 410 fixed at a distal end thereof to a shaft420 having a tip 422. A cable 415 couples the probe 400 to a source ofmicrowave ablation energy (not shown). A directional reflector assembly405 includes a tubular shaft 440 and a conical aperture 442. Shaft 440includes a coupling 425 having one or more slots 445 defined thereinthat are adapted to engage a protrusion 430 provided at a proximal end421 of a probe shaft 420. The engagement of slot 445 with protrusion 430may aid the positioning of outer tube 440 with probe shaft 420, and mayadditionally, or alternatively, provide positive retention of outer tube440 to probe shaft 420 during use. Slot 445 and protrusion 430 mayinclude a bayonet arrangement, as shown, and may additionally, oralternatively include any suitable coupling arrangement, such as withoutlimitation, a threaded arrangement, an interference fit arrangement, orother coupling arrangement. Coupling 425 may additionally, oralternatively, be configured to provide coolant coupling (e.g., fluid orgas coupling) between the probe handle 410 and/or shaft 420, and adirectional reflector assembly.

FIG. 17 shows an embodiment of an air-filled directional reflectorassembly 260 that includes an outer tube 261 having a distal end 264 anda proximal end 265 that is dimensioned to slideably engage a probe shaft(e.g., 420). Outer tube 261 may be formed from any suitable material,including without limitation metallic material (e.g., stainless steel)and/or dielectric material (e.g., epoxy fiber composite). A conicalaperture 262 having a distal base opening 263 and a proximal apexopening 268 is joined at a proximal apex opening 268 thereof to a distalend 264 of shaft 261. For use, the directional reflector assembly 260 ispositioned onto a recipient microwave ablation probe (not shown) bysliding a distal end of the probe into a proximal inner portion 266 ofouter tube 261. A generally circular distal plate (not shown) having acircular opening disposed at a center thereof is fixed at a perimeterthereof to a distal open base of conical aperture 262.

Turning to FIG. 18, an embodiment of a dielectric-filled directionalreflector assembly 270 in accordance with the present disclosure isshown. Directional reflector assembly 270 includes an outer tube 271having a distal end 276 and a proximal end 277 that is dimensioned toslideably engage a probe shaft as previously described herein. Outertube 271 may be formed from any suitable material, as previouslydescribed herein. A conical reflector 272 having a distal base opening273 and a proximal apex opening 278 is joined at the proximal apexopening 278 to a distal end 276 of shaft 271. Conical reflector 272includes a dielectric core 279 disposed therein. An inner opening 274defined within outer tube 271 is coupled to an inner opening 275 axiallydefined within dielectric core 279. An inner diameter of outer tube 271(e.g., corresponding to the diameter of inner opening 274) issubstantially equal to an inner diameter of inner opening 275 to form asubstantially continuous opening 274 between tube 271 and a distal endof dielectric core 279 to accommodate the insertion of an ablation probethereinto for use, as previously described herein.

In yet another embodiment according to the present disclosure shown inFIG. 14, a multilayer dielectric-filled directional reflector assembly280 includes an outer tube 281 having an inner opening 284 definedlongitudinally therein. A conical reflector 282 is joined at a proximalopen apex end thereof to a distal end of outer tube 281. Conicalreflector 282 includes at least a first dielectric core region 2831,that may be formed from a first dielectric material, and a seconddielectric core region 2832, that may be formed from a second dielectricmaterial. Additional dielectric core regions beyond a first and secondare envisioned within the scope of the present disclosure, e.g.,dielectric core region 2833. The dielectric core regions 2831 et seq.may have a flared conical shape and may be arranged such that thedielectric regions 2831 et seq. are coaxially disposed, as shown in FIG.14. Additionally, or alternatively, the dielectric core regions may haveother shapes and arrangement, including but not limited to, planar,interleaved, toroidal, radial, cylindrical, and polygonal extrusions.

An inner opening 284 defined within outer tube 281 is coupled to aninner opening 285 axially defined through the innermost multilayerdielectric core region, e.g., 2833. An inner diameter of outer tube 281(e.g., corresponding to the diameter of inner opening 284) issubstantially equal to an inner diameter of inner opening 285 to form asubstantially continuous opening 284 between tube 281 and a distal endof multilayer dielectric core 2831 et seq. to accommodate the insertionof an ablation probe therein for use, as previously described herein.

Turning now to FIG. 20, a multilayer dielectric-filled directionalreflector assembly 290 includes a tubular shaft 291 having an inneropening 294 defined longitudinally therein. A conical reflector 292 isjoined at a proximal open apex end thereof to a distal end of tubularshaft 291. A generally circular distal plate 298 having a circularopening 299 disposed at a center thereof is fixed at a perimeter thereofto a distal open base of reflector 292. Circular distal plate 298 may beformed from material that is radiofrequency transparent at an operatingfrequency of a microwave ablation probe, which may be in a range ofabout 915 MHz to about 2.45 GHz. Circular distal plate 298 mayadditionally, or alternatively, be formed from a lubricious material,including without limitation, polytetrafluoroethylene (a.k.a. PTFE orTeflon®, manufactured by the E.I. du Pont de Nemours and Company ofWilmington, Del., United States).

Conical reflector 292 includes one or more dielectric core regions,e.g., 2931, 2932, 2933. The dielectric core regions 2931, 2932, 2933 etseq. may be formed from similar, or from dissimilar, dielectricmaterials. The dielectric core regions 2931 et seq. may have a flaredconical shape and may be arranged coaxially, radially, or may have othershapes and arrangements, including but not limited to, planar,interleaved, toroidal, cylindrical, and polygonal extrusions. Alongitudinal inner opening 294 defined within tubular shaft 291 iscoupled to an inner opening 295 axially defined through an innermostdielectric core region, e.g., 2933. An inner diameter of tubular shaft291 (e.g., corresponding to the diameter of inner opening 294) may besubstantially equal to an inner diameter of inner opening 295 and tocircular opening 299 to form a substantially continuous opening 294between tube 291 and a distal surface of circular distal plate 298 toaccommodate the insertion of an ablation probe therein for use, aspreviously described herein.

FIG. 21 illustrates yet another embodiment wherein a directionalreflector assembly 300 includes a dual-wall cooled shaft 301. The cooledshaft 301 includes an inner tube 309 coaxially disposed within an outertube 308 having a cooling region 307 disposed therebetween. Coolingregion 307 may include thermally-conductive material (e.g., copper)and/or heat pipe that is adapted to transfer thermal energy from theshaft 301 and/or a conical reflector 302 by conduction or convection.Cooling region 307 may additionally, or alternatively, include fluidcoolant. Examples of coolant include, but are not limited to, liquidssuch as deionized water, or saline. Gaseous coolant (e.g., air orbiocompatible refrigerant) may also be utilized. Cooling region mayextend distally into conical reflector 302 along a channel 305 definedbetween an outer surface of inner tube 309 and an inner surface of aninnermost dielectric core region, e.g., 3033. A generally circulardistal plate 306 having a circular opening 3061 disposed at a centerthereof is fixed at a perimeter thereof to a distal open base ofreflector 302. Circular distal plate 306 may be formed from materialthat is radiofrequency transparent and/or lubricious as previouslydescribed herein. Conical reflector 302 may include one or moredielectric core regions, e.g., 3031, 3032, 3033 et seq. as previouslydescribed, which may be formed from similar, or from dissimilar,dielectric materials. Inner tube 309 extends distally into conicalreflector 302 to form a continuous opening 304 defined axially withinthe directional reflector assembly 300, e.g., from a proximal end ofshaft 301 to a distal surface of cover 306 to accommodate the insertionof an ablation probe therein for use, as previously described.

With reference now to FIG. 22, a fluid-cooled directional reflectorassembly 310 includes a dual-wall cooled shaft 311 having an outer tube318, an inner tube 317 coaxially disposed therein and defining anopening 314, and a fluid path 319 defined therebetween. A conicalaperture 312 is joined to a distal end of the outer tube 318. Conicalaperture 312 includes a dielectric 313 disposed therein. A coolingchamber 315 having a proximal end in fluid communication with a distalend of fluid path 319 is defined within the dielectric 313. A generallycircular distal plate 316 having a circular opening 3162 defined at acenter thereof is fixed at least at a perimeter 3161 thereof to a distalrim 3121 of an open base of reflector 312 and adapted to form a sealeddistal end of cooling chamber 315. Circular distal plate 316 mayadditionally, or alternatively, be joined at the center thereof to anouter surface and/or distal end of inner tube 317. During use, coolantmay circulate through fluid path 319 and or cooling chamber 315, whichmay help control the temperature of the attachment 310, and may providedielectric loading within the aperture 312. Circular distal plate 316may be formed from fluid-impermeable material that is radiofrequencytransparent and/or lubricious, such as without limitation, PTFE.

As shown in FIG. 23, a fluid-cooled directional reflector assembly 320may include a conical aperture 322 having a cooling chamber 325 definedtherein by the interior volume of the aperture 322 and a circular distalplate 326. Circular distal plate 326 is fixed at an outer perimeter 3261thereof to a distal rim 3221 of conical aperture 322. Circular distalplate 326 may additionally, or alternatively, be fixed at a perimeter ofan opening 3262 define therein to a distal outer surface of inner tube327.

FIG. 24 depicts a fluid-cooled directional reflector assembly 330 havinga single-walled tubular shaft 331 defining an opening 332 therein andjoined at a distal end thereof to a proximal open apex 333 of conicalaperture 332. A circular distal plate 336 fixed at an outer perimeter338 thereof to a distal rim 335 of conical aperture 322 to define acoolant chamber 339 within the conical aperture 322. Circular distalplate 336 additionally, or alternatively, includes an opening 337defined therein that is joined at a perimeter thereof to a distal outersurface of tubular shaft 331. Coolant chamber 339 contains coolant 3391,for example, and without limitation, saline, sterile water, and/ordeionized water, which may enhance cooling and/or improve dielectricloading during use.

A directional reflector assembly in accordance with the presentdisclosure may include one or more baluns, which may improve theradiation and/or ablation pattern provided during use. Moreparticularly, and with reference now to FIG. 25, a directional reflectorassembly 340 includes a tubular shaft 341 defining an opening 344therein and joined at a distal end thereof to a proximal open apex 343of a conical aperture 342. A circular distal plate 346 is disposed at adistal open end of the conical aperture 342 in a manner previouslydescribed herein. A dielectric core 347 is disposed within the conicalaperture 342. A balun 345 is concentrically disposed around at least apart of tubular shaft 341, e.g., along a distal portion of the shaft 341and substantially adjacent to the proximal open apex 343 of the conicalaperture 342. Balun 345 may include a ring-like balun short 349concentrically disposed around the shaft 341 at a proximal end of thebalun 345 and electrically coupled thereto. A balun dielectric layer 348may additionally, or alternatively, be concentrically disposed betweenthe balun 345 and the shaft 341.

In yet another embodiment shown in FIG. 26, an air-filled directionalreflector assembly 350 includes a tubular shaft 351 defining an opening354 therein and joined at a distal end thereof to a proximal open apex357 of a conical aperture 352. A first balun 355 is concentricallydisposed around at least a part of tubular shaft 351, e.g., along adistal portion of the shaft 351 and substantially adjacent to theproximal open apex 357 of the conical aperture 352. First balun 355 mayinclude a ring-like balun short 359 concentrically disposed around theshaft 351 at a proximal end of the balun 355 and electrically coupledthereto. A first balun dielectric layer 358 may additionally, oralternatively, be concentrically disposed between the balun 355 and theshaft 351. Conical aperture 352 includes a second balun dielectric layer353 disposed between an inner surface of conical aperture 352 and asecond balun 356. First balun 355 and second balun 356 may beelectrically coupled.

FIG. 27 illustrates still another embodiment in accordance with thepresent disclosure that may include a shaft balun, a cone balun, and/ora dielectric core. In more detail, a dielectric core directionalreflector assembly 360 includes a tubular shaft 361 that is joined at adistal end thereof to a proximal open apex 370 of a conical aperture362. A first balun 365 is concentrically disposed around at least a partof tubular shaft 361, e.g., along a distal portion of the shaft 361 andsubstantially adjacent to the proximal open apex 370 of conical aperture362. First balun 365 may include a ring-like balun short 369concentrically disposed around the shaft 361 at a proximal end of thebalun 365 and electrically coupled thereto. A first balun dielectriclayer 368 may additionally, or alternatively, be concentrically disposedbetween the balun 365 and the shaft 361. Conical aperture 362 includes asecond balun dielectric layer 363 disposed between an inner surface ofconical aperture 362 and a second balun 366. First balun 365 and secondbalun 366 may be electrically coupled. Conical reflector 362 includes adielectric core 367 disposed therein, e.g., within an inner surface ofsecond balun 366. An inner opening 364 defined within outer shaft 361 iscoupled to an inner opening 371 axially defined within dielectric core367. An inner diameter of outer shaft 361 (e.g., the diameter of inneropening 364) is substantially equal to an inner diameter of inneropening 371 to form a substantially continuous opening 364 between aproximal end of outer shaft 367 and a distal end of dielectric core 361to accommodate the insertion of an ablation probe thereinto for use, aspreviously described herein.

The above-described directional reflector assemblies and electrosurgicaldevices for treating tissue and methods of directing electromagneticradiation to a target volume of tissue may be used to providedirectional microwave ablation, wherein the heating zone may be focusedto one side of the electrosurgical device, thereby allowing cliniciansto target small and/or hard tumors without having to penetrate the tumordirectly or effect more healthy tissue than necessary. The presentlydisclosed electrosurgical devices and directional reflector assembliesmay allow clinicians to avoid ablating critical structures, such aslarge vessels, healthy organs or vital membrane barriers, by placing theelectrosurgical device between the tumor and critical structure anddirecting the electromagnetic radiation toward the tumor and away fromthe sensitive structure.

Although embodiments have been described in detail with reference to theaccompanying drawings for the purpose of illustration and description,it is to be understood that the inventive processes and apparatus arenot to be construed as limited thereby. It will be apparent to those ofordinary skill in the art that various modifications to the foregoingembodiments may be made without departing from the scope of thedisclosure.

1-20. (canceled)
 21. A directional reflector assembly for use with anelectrosurgical device, comprising: a tubular inner shaft having aproximal portion and a distal portion, the tubular shaft defining alumen adapted to operably engage an electrosurgical ablation probe; atubular outer shaft concentrically-disposed about the tubular innershaft; a conical aperture including: a proximal open apex coupled to adistal portion of the tubular outer shaft; a distal open base; and aninterior volume defined between the proximal open apex and the distalopen base, the interior volume of the tubular inner shaft being in fluidcommunication with the conical aperture.
 22. The directional reflectorassembly according to claim 21, wherein the distal portion of thetubular inner shaft extends into the open distal base of the conicalaperture.
 23. The directional reflector assembly according to claim 21,further comprising a coolant chamber defined within the conicalaperture.
 24. The directional reflector assembly according to claim 23,further comprising a fluid conduit defined between the tubular innershaft and the tubular outer shaft.
 25. The directional reflectorassembly according to claim 24, wherein the fluid conduit is in fluidcommunication with the cooling chamber.
 26. The directional reflectorassembly according to claim 21, further comprising: a circular platecoupled to the distal open base of the conical aperture, the circularplate including an opening aligned with the lumen.
 27. The directionalreflector assembly according to claim 26, wherein the circular plate isformed from a dielectric material.
 28. The directional reflectorassembly according to claim 21, wherein at least one of the tubularinner shaft or the tubular outer shaft includes at least one slotadapted to operably engage a corresponding protrusion of theelectrosurgical ablation probe.
 29. The directional reflector assemblyaccording to claim 21, wherein a dielectric material is disposed withinthe interior volume of the conical aperture.
 30. The directionalreflector assembly according to claim 29, wherein the dielectricmaterial includes a plurality of dielectric materials, wherein each ofthe dielectric materials has a dielectric property and the dielectricproperties of the dielectric materials are different from one another.31. The directional reflector assembly according to claim 29, furthercomprising a cooling aperture defined between an outer surface of thetubular inner shaft and the dielectric material.
 32. The directionalreflector assembly according to claim 31, wherein the cooling apertureis in fluid communication with a fluid conduit defined between thetubular inner shaft and the tubular outer shaft.
 33. The directionalreflector assembly according to claim 32, further comprising a fluidcirculating through the cooling aperture, wherein the fluid conduit andthe fluid form a dielectric loading within the conical aperture.
 34. Thedirectional reflector assembly according to claim 24, wherein the fluidconduit is formed from a thermally-conductive material.
 35. Thedirectional reflector assembly according to claim 24, further comprisinga heat pipe in thermal communication with the fluid conduit, the heatpipe configured to transfer thermal energy from the outer shaft to thefluid conduit.